We propose to use a mouse model of allergen induced airway remodeling to investigate the contribution of mast cells to airway remodeling, as well as to understand the mechanism by which mast cell progenitors traffic from the bone marrow to the lung and contribute to airway remodeling. In particular we hypothesize that mast cell derived TNF plays a central role in mediating allergen induced airway remodeling through effects on airway smooth muscle, as well as through recruitment of mast cell progenitors and eosinophils to the lung. To test this hypothesis we plan to determine levels of allergen induced airway remodeling in WT mice and compare this to levels noted in mutant mice (mast cell deficient, TNF deficient), as well as mast cell deficient mice reconstituted with TNF deficient mast cells. In addition, we have utilized cre/lox molecular techniques to generate mice deficient in the ability to activate NF-kB in airway epithelium. As these mutant mice exhibit reduced numbers of peribronchial mast cells, they will be utilized to investigate the role of NFkB regulated genes in airway epithelium contributing to mast cell progenitor trafficking to the remodeled airway. Overall, these studies will provide insight into the mechanism by which mast cell derived TNF contributes to airway remodeling, as well improve our understanding of the mechanism by which NF-kB regulated genes in airway epithelium direct mast cell progenitor trafficking from the bone marrow to the lung and contribute to airway remodeling. TNF is a protein that is highly expressed in the airway in asthmatics with ongoing symptoms of asthma. Our studies in a mouse model will shed light on whether therapies targeting TN in asthma may provide a novel strategy to reduce airway scarring in severe asthmatics.